Pipes, especially relatively small diameter copper pipes between one half inch and two inches nominal diameter, are used extensively to provide water service for homes, business and industry. Such pipes may be sealingly joined to one another end to end using mechanical couplings to create a piping network for conveying water throughout a building such as a home, office or factory.
Mechanical couplings provide various advantages over traditional solder joints for connecting pipes in that they avoid the use of acid flux, solder and open flame to effect a connection. Assembly of a joint using a mechanical coupling also requires less time than a solder joint and may be performed by a less skilled worker. Assembly of a joint merely requires that a pipe end be inserted into a coupling so that the coupling and pipe end engage properly.
The mechanical coupling, which may be a fitting such as an elbow, tee or straight fitting, for example, includes a housing having a socket coaxially aligned with a receptacle for receiving the pipe end. A sealing member, such as an O-ring or a pressure responsive seal and a retainer are captured within the receptacle adjacent to the socket. The retainer may have a plurality of flexible teeth that extend around the circumference of the receptacle. The teeth project radially inwardly and are angularly oriented toward the socket. When the pipe end is inserted through the receptacle and into the socket, the teeth engage the pipe's outer surface and retain it within the coupling. Due to their angular orientation, the teeth are “self jamming” and resist motion of the pipe that would tend to force it from the receptacle. The sealing member within the receptacle engages the pipe and the housing to provide a fluid-tight seal, and the socket supports the pipe and provides bending stiffness to the joint, preventing angular deflection between the pipe and the coupling.
To ensure an effective, fluid-tight joint, the pipe end must be properly seated within the coupling so that it engages the socket over a sufficient length to insure that the full stiffness of the joint is achieved and so that the sealing member and the pipe outer surface engage and seal relatively to one another. Furthermore, the teeth of the retainer must engage the pipe end to ensure that it is retained within the coupling against the fluid pressure it will eventually see. However, without a visible means to indicate proper engagement of the pipe end with the mechanical coupling it is difficult to be sure that the joint formed will be fluid tight and sufficiently inserted to maximize bending stiffness and strength of the joint. Visible indicators may take the form of “witness marks”, typically circumferential grooves or other visible markings that extend around the pipe in spaced relation to the end. The witness mark is positioned, for example, such that if it is not positioned visible and flush next to the coupling, then the pipe end is not properly engaged with the coupling and must be further inserted until the witness mark is visibly flush with the coupling. It is advantageous to provide a device that will prepare pipe ends for joining with mechanical couplings, for example, by forming one or more witness marks in proper spaced relation to an end of a pipe for a particular coupling and diameter pipe.